1. Field of the Invention
The present invention relates to an optical device including a light source, and an optical element through which light from the light source passes.
2. Description of Related Art
Conventionally, there have been developed and manufactured optical pickup devices for recording or reproducing information on or from various optical discs such as CDs (Compact Discs), DVDs (Digital Versatile Discs), and BDs (Blu-ray Discs).
For example, as shown in JP 2008-305516 A, such an optical pickup device includes a light source (for example, a semiconductor laser), and an optical element (for example, an objective lens) through which light emitted from the light source passes. The optical element is fixed with an adhesive to the device body or its components such as a lens holder of an objective lens driving device. The adhesive is a resin that can be cured by ultraviolet light (UV-curable resin).
Conventionally, glass has been used as a material for optical elements. Recently, however, plastic has been used as a material for optical elements, in response to a demand for cost reduction in optical pickup devices.
With an increase in the capacity of optical discs, short-wavelength lasers have been used as light sources. For example, an infrared laser with a center wavelength of 780 nm is used as a light source for CDs. A red laser with a center wavelength of 650 nm is used as a light source for DVDs. A blue-violet laser with a center wavelength of 405 nm is used as a light source for BDs.